This section describes background subject matter related to the disclosed embodiments of the present invention. There is no intention, either express or implied, that the background art discussed in this section legally constitutes prior art.
In chemical processing which relies on fluid handling in general, and particularly when the fluids to be handled are toxic, hazardous and potentially reactive with materials of construction or ambient air. Improved system leak reliability and careful integration of the fluid handling devices into a network architecture which makes up the fluid handling system is of paramount importance. In addition, it is important that all of the component devices used in the fluid handling be well integrated into the overall fluid flow network architecture, to ensure system leak reliability, provide a compact size, and enable flexible control. In applications such as semiconductor processing, for example, the fluid component devices must also exhibit particular capabilities which ensure cleanliness of the fluid delivery process, so that the solid state devices being fabricated will not be contaminated, affecting performance and reliability.
As discussed in related U.S. Pat. No. 6,736,370 to Crockett et al., issued May 18, 2004, and entitled: “Diaphragm Valve With Dynamic Metal Seat And Coned Disk Springs”, to ensure that particles will not be generated by the fluid delivery apparatus, it is important that the interior surface of fluid flow channels be smooth, and without sharp corners which can wear down and act as a source of particulates. In addition, it is important that the material which forms the fluid flow channels not be corroded by a fluid which passes through the fluid flow channels, and that there not be dead space in the channels which would permit corrosion and act as a source of hazardous material when the fluid flow system is shut down for maintenance.
In semiconductor processing equipment, it is critical that the fluid flow system not leak; further, gases such as hydrogen and helium are commonly handled by the fluid delivery system. Hydrogen is the lightest element and is found in nature as a colorless, odorless, highly flammable gas in the molecular form H2. Hydrogen leaking from a pinhole leak in a piping system can ignite and burns with a nearly invisible blue flame which is highly dangerous to someone walking by. Helium is also a light weight, small atom, which is typically used for leak testing because of its small atomic size, diffusivity and high mobility. While a leak of Helium is not as dangerous as a leak of hydrogen, the fluid flow system must be adequate to contain helium without a substantial leak. The general semiconductor industry standard for a helium leak is as little as about 1×10−9 cc/sec. of helium at a pressure differential of one atmosphere. A fluid flow system which can meet this helium leak requirement is indicative of the ability to prevent exposure of the environment to often extremely toxic and corrosive process fluids. Due to the toxicity of a number of the fluids transported, very high system leak reliability and long service life (avoidance of the need to shut down and change out parts) are of great importance. Also of importance are a compact design, and a reasonable cost.
In related U.S. patent application Ser. No. 10/617,950 of Crockett et al., filed Jul. 12, 2003, entitled: “Micromachined Integrated Fluid Delivery System With Dynamic Metal Seat Valve And Other Components”, general concepts are provided regarding an integrated fluid flow system with high levels of device integration which permits not only improved functionality, but also considerable cost savings in fabrication. As described in the '950 patent application, as a result of reduced fabrication cost, and a properly balanced level of modularity, it is possible to reduce maintenance costs for the fluid flow system by replacing integrated modules rather than shutting the system down for long maintenance and repair operations with respect to individual component devices (which are part of the integrated module in present designs).
With respect to an integrated network architecture of fluid flow devices and channels with an integrated control system, there is a constant need for a higher degree of integration, simplification and ease of operation. In addition to performance and handling advantages, the integrated fluid flow system must be cost competitive. This means that fabrication methods for the various fluid handling devices, interconnecting network architecture and integrated control system need to be easily scalable in tooling for mass production, variable production demand and cost-effective NRE (Non-recurring Engineering) charges. The present invention provides substantial advantages in all of these areas.
There are a number of U.S. patents which pertain to gas sticks of the kind which are frequently used in the semiconductor industry to transport fluids to and from semiconductor processing chambers and apparatus which is used in conjunction with the processing chambers. These gas sticks are typically fabricated from machined blocks of corrosion resistant material. Some examples of U.S. patents which pertain to gas sticks include: U.S. Pat. No. 5,303,731, issued Apr. 19, 1994, entitled “Liquid Flow Controller”, which describes the body block of a fluid flow controller which has conduits machined in it. U.S. Pat. No. 5,605,179, issued Feb. 25, 1997, entitled “Integrated Gas Panel”, which describes a plurality of individual gas process modules coupled together with a plurality of gaskets located between them; where the modules are coupled together such that respective ports of each module are in fluid communication with one another to form a common tube or port. U.S. Pat. No. 5,730,181, issued Mar. 24, 1998, entitled “Mass Flow Controller with Vertical Purifier”, which describes a purifier which includes a purifier metal block, a mass flow meter block, and a valve block, where sealing between the blocks is with a “z” seal, and each block has machined fluid flow conduits in it. U.S. Pat. No. 5,836,355, issued Nov. 17, 1998, entitled “Building Blocks for Integrated Gas Panel”, which describes a gas panel comprising a plurality of discreet blocks, where gas tubing is replaced by stacked blocks which have a series of conduits oriented at different directions which are designed to be used with other blocks to form a fluid pathway. U.S. Pat. No. 5,992,463, issued Nov. 30, 1999, entitled “Gas Panel”, which describes a one piece manifold body which has at least one lateral wall extending in the general direction of gas flow. The lateral wall includes at least one active device site (to which an active device is attached) having an active device thereon (a series of openings and conduits are machined into the manifold).
These gas sticks typically include components and manifolds which are fabricated from machined blocks of corrosion resistant material. Gas sticks of this kind are costly to fabricate, and frequently the machined manifolds are a source of particulates which are generated as fluids flow over a rough surface or around elbow corners which are created by the machining process.
Axially loaded diffusion bonding techniques have been developed for use in the manufacture of heat exchangers; gas turbine engine aerofoils such as fan blades, and compressor blades; and, separation column devices for use in gas or liquid phase sample analysis, for example. The technique used for axially-loaded diffusion bonding is very closely related to the device which is being fabricated. The diffusion bonding conditions depend on the materials to be diffusion bonded, the complexity of the shape of the device which is being fabricated, and the performance criteria for the diffusion bonded device. Due to the difficulty in obtaining a uniformly diffusion bonded article, other means of holding elements of a device together, such as brazing or application of an adhesive, for example, are used when the application will permit.
In addition to axially-loaded diffusion bonding, another form of diffusion bonding may be used to produce laminated parts. Hot Isotactic Pressing (HIP) is said to be particularly suited for the bonding of dissimilar materials. Dissimilar materials such as silicon nitride, Incoloy 909, austenitic steel, ferritic steel, zirconia, and zirconia-hydroxyapatite are said to have been bonded using HIP techniques. A series of published papers is available with respect to the joining of cemented carbides of the kind using for tooling applications. A HIP diffusion bonding technique is sometimes recommended as an alternative to axially-loaded diffusion bonding. However, the HIP diffusion bonding (an iso-static loaded technique) requires different, more complex fixturing. Both processes fall under the broad category of diffusion bonding.
Diffusion bonding techniques commonly use interlayers to ensure good contact between the bonding surfaces and that bond strengths close to the bulk strength of the material are obtained in the bonding process. At the same time, interlayers are not recommended in cases where high tolerances are required by the component design
The present invention is related to diffusion bonded substrates which include fluid flow conduits. These fluid flow conduits preferably are formed from etched plates which are designed, when combined, to produce complex shaped fluid flow conduits when necessary, and to produce rounded surfaces when a conduit turns or twists to accommodate devices which are mounted on or contained within the substrate. The diffusion bonded substrates provide the advantage of reduced dead space and generation of fewer particulates; however, the diffusion bonding process requires careful control of process materials and processing conditions to produce an acceptable bonded part.
A detailed review of the documents discussed above and other publications and patents which describe diffusion bonding as a fabrication technique for particular devices makes it clear that the fabrication method used depends considerably on the design of the device which is required to perform the device function, and on the materials from which the device is constructed. In the present instance, the device may be any fluid flow device which is used as a part of semiconductor fabrication equipment.